Rational Construction of Self‐Standing Sulfur‐Doped Fe2O3 Anodes with Promoted Energy Storage Capability for Wearable Aqueous Rechargeable NiCo‐Fe Batteries

Abstract Aqueous rechargeable Ni‐Fe batteries featuring an ultra‐flat discharge plateau, low cost, and outstanding safety characteristics show promising prospects for application in wearable energy storage. In particular, fiber‐shaped Ni‐Fe batteries will enable textile‐based energy supply for wearable electronics. However, the development of fiber‐shaped Ni‐Fe batteries is currently challenged by the performance of fibrous Fe‐based anode materials. In this context, this study describes the fabrication of sulfur‐doped Fe 2 O 3 nanowire arrays (S‐Fe 2 O 3 NWAs) grown on carbon nanotube fibers (CNTFs) as an innovative anode material (S‐Fe 2 O 3 NWAs/CNTF). Encouragingly, first‐principle calculations reveal that S‐doping in Fe 2 O 3 can dramatically reduce the band gap from 2.34 to 1.18 eV and thus enhance electronic conductivity. The novel developed S‐Fe 2 O 3 NWAs/CNTF electrode is further demonstrated to deliver a very high capacity of 0.81 mAh cm −2 at 4 mA cm −2 . This value is almost sixfold higher than that of the pristine Fe 2 O 3 NWAs/CNTF electrode. When a cathode containing zinc‐nickel‐cobalt oxide (ZNCO)@Ni(OH) 2 NWAs heterostructures is used, 0.46 mAh cm −2 capacity and 67.32 mWh cm −3 energy density are obtained for quasi‐solid‐state fiber‐shaped NiCo‐Fe batteries, which outperform most state‐of‐the‐art fiber‐shaped aqueous rechargeable batteries. These findings offer an innovative and feasible route to design high‐performance Fe‐based anodes and may inspire new development for the next‐generation wearable Ni‐Fe batteries.